The Northern California Family Registry, the leader of Research Module 3, proposes to enrich the Cooperative Family Registry of Breast Cancer Studies (CFRBCS) with additional minority families. Of the over 5,000 families currently enrolled in the CFRBCS, about 12% are minorities, most of which were recruited in the San Francisco Bay area. In collaboration with all Family Registries participating in the CFRBCS (except Australia) and a new Family Registry to be established in Southern California, an additional 1,700 population-based and 550 clinic- based minority families will be added to CFRBCS, including African- Americans, Hispanics, Chinese, Japanese and Filipinos. Using the protocols and questionnaires developed for the current CFRBCS, each Registry will continue the collection of family history, epidemiological, diet, treatment, and follow-up data and biospecimens such as blood or mouthwash samples and tumor blocks. BRCA1 and BRCA2 mutation testing will be performed at each Registry. The specific aims of the proposed Research Module 3 are to: (1) estimate the prevalence of BRCA1 and BRCA2 mutations in each racial/ethnic group and identify the spectrum of mutations (including founder mutations) in population- based samples of breast cancer patients; (2) estimate the risk of breast cancer among BRCA1 and BRCA2 mutation carriers (penetrance); (3) contribute minority families to the CFRBCS to support the research proposed by the other Modules; and (4) contribute the minority families to the CFRBCS to support the research proposed by the other Modules; and (4) contribute the minority families to the CFRBCS for future collaborative studies. The Northern California Family Registry will recruit an additional 1,060 minority families t o bring the total number of minority families enrolled in CFRBCS by the year 2005 to 3,000, including 2,300 population-based and 700 clinic-based families. CFRBCS will be the largest resource ever assembled to support genetic and molecular research of breast cancer in minority families. Such an effort is unprecedented and unique, as no single center would ever be able to assemble such large numbers of minority from five racial/ethnic groups.